There are few bands that manage to define a music genre, but when they do, they pave the road for bands to come. Alternative rock band Radiohead paved the way for countless alternative rock bands and created a musical niche of its own because of its unique, cutting-edge sound.

Now I won’t get too far into Radiohead’s illustrious career, but with the release of the band’s sophomore album “The Bends,” the band — formerly a one-hit wonder with the song “Creep” — burst into the limelight. The twin masterpieces of the titanic “OK Computer” in 1997 and the digital alienation of “Kid A” in 2000 followed, confirming the band’s greatness. But fast-forward to the mid-2000s and you could argue that Radiohead was starting to decline. They had released “Amnesiac” and “Hail to the Thief” to acclaim but not to the level of their predecessors. Having completed their contract with EMI, they went on hiatus. For the first time, the quintet of vocalist Thom Yorke, guitarists Jonny Greenwood and Ed O’Brien, bassist Colin Greenwood, and drummer Phil Selway were taking a break.

The band had written songs, some of which would end up on “In Rainbows,” but couldn’t figure out what to do with them. Early studio sessions with producer Mark Stent instead of longtime producer Nigel Godrich were deadlocked. Yorke announced his debut solo album, “The Eraser,” in May 2006, shortly after the yearlong Stent sessions proved fruitless. The situation appeared so dire that Radiohead’s own management suggested that the band break up. Luckily, Radiohead didn’t listen. Instead, they decided to test their new, unfinished and reworked material on the road. It was an ingenious move for a generally insular and studio-oriented band, and it showed that “In Rainbows” was going to be different right down to its foundation.

The band returned in October 2006 with plenty of material to record, produced by Neil Godrich once again. So many songs were developed that an eight-track bonus disc of songs from the “In Rainbows” sessions was released 18 months after the original album. There was just one problem: Radiohead no longer had a record deal, let alone a major label such as EMI. The usual guidelines of promotion and distribution were useless for “In Rainbows.” A normal band would likely cave and sign a deal, but Radiohead knew how to use one force that had put the mainstream recording industry in steep decline: the Internet. To quote Yorke in an interview with Wired: “Every record for the last four — including my solo record — has been leaked. So the idea was like, ‘we’ll leak it, then.’”

This idea became the “Pay-What-You-Want” model for the initial release of “In Rainbows” in October 2007. Fans could get the album from Radiohead directly through the Internet and pay whatever they want (or nothing at all). They could also pre-order a hefty vinyl release at a steep price. The experiment was groundbreaking and opened new avenues for the Internet as a music-sharing entity. The band did eventually follow through with a physical release, but it was with TBD Records, a tiny imprint that had formed in the summer of 2007. Essentially, the band had found the antithesis of selling out. The bold distribution move sparked such a debate that an ordinary album might be overshadowed.

Thankfully, “In Rainbows” has lasted not just as an economic curiosity but as a standout record, even in Radiohead’s cluttered catalog. The album follows the lead of “Thief” in its return to guitar-led songs. The hyperactive yet haunting “Bodysnatchers” ranks among the fastest and loudest songs in Radiohead’s history. “Weird Fishes/Arpeggi” and “Jigsaw Falling into Place” fall into a similar up-tempo vein with ghostly vocals, a combination that Radiohead manages to make sound strangely beautiful. However, there’s another feeling on “In Rainbows” that is very unusual for Radiohead: warmth, sometimes influenced by rhythm and blues. Sure, the band is still about social alienation and ominous atmospherics, but those landscapes are no longer as jagged. In fact, they can be quite comforting, as in “House of Cards,” where Yorke cryptically describes a sexually intimate relationship. Who knew that Radiohead would make a song where the line “Infrastructure will collapse” is vaguely sensual instead of apocalyptic? “Nude” makes a similar juxtaposition with lyrics about not getting any big ideas, but it then takes off with a series of circular, wordless coos from Yorke.

Perhaps the most satisfying thing about “In Rainbows” is the knowledge that the band can go in several different directions at any time, be it a three-guitar attack or fractious, digital pseudo-R&B centered on Selway’s impeccable rhythms and Yorke’s ethereal falsetto. This album distills those possibilities with new colors added and new ways to explore their sound. The fact that nearly 15 years into their career, Radiohead was able to surprise yet ultimately be rewarding is quite an accomplishment. After all, the band has never strayed from its niche, no matter where it has been on the spectrum.